Overhauling commutators of dynamoelectric machines



Dec. 17, 1963 OVERHAULING COMMUIATORS OF DYNAMOELECTRIC MACHINES Filed Oct. 9, 1961 United States Patent Filed Oct. 9, 1961, Ser. No. 143,890 3 Claims. (Cl. 51244) The present invention relates to the art of overhauling the commutators of dynamo-electric machines, and particularly to abrading or sanding such commutators for the purpose of cleaning them and removing oxide coatings therefrom to improve the electrical contact between the commutators and its cooperating brushes.

When abrading the brush contact surfaces. of commutators of rotary electric generators or motors, it is of course important to maintain the surface as a true circle, and not to trim the segments unevenly so as to change the cylindrical surface from its true circular relation to the center of rotation of the armature upon which it is mounted. In order to avoid such alterations in the commutator, it has heretofore been customary to provide rather elaborate centering machines for rotating the armature on its true center, thereby enabling a uniform abrading operation on the commutator without upsetting the center relation of the commutator to the axis of rotation of the armature.

A -The present invention provides a very simple, efiicient, and inexpensive expedient for abrading armature commutators, and insuring against alteration either of the true circular contour of the commutator surface, or the axial center of said contour, all Without requiring any special centering equipment for mounting the armature. The housings of many electrical generators and motors are provided with removable end frames adjacent the commutator end of the armature. These end frames carry a bearing which receives and rotatively supports one end of the armature shaft, and this bearing in cooperation with the end of the armature shaft defines the true center of rotation of the armature. ent invention, the end frame is removed from the housing and is utilized to mount one or more strips of abrasive paper or fabric. The armature is also removed from the housing and held in any convenient manner, as in a conventional rise. The end frame is thereupon mounted by means of its bearing on the end of the armature shaft to place the abrasive fabric in abrading relation to the circumferential surface of the commutator. The end frame may now be turned on the armature shaft, providing a center of rotation coincident with the axial center of the commutator, to apply a uniform and equal abrading action over the entire circumference of the commutator. After the desired amount of abrading is completed, the end frame is removed from the armature, the abradant dust cleaned from the commutator, the armature returned to the motor or generator housing, the abrading fabric removed from the end frame, and the end frame reassembled on the motor or generator housing.

It is accordingly one object of the present invention to provide for the abrading of commutators of dynamo-electric machines.

Another object of the present invention is to provide for the abrading of commutators of dynamo-electric machines, utilizing the structure of the machine itself to obtain a'guide for the center of movement of the abradant around the surface of the commutator in coincidence with the center axis of the commutator.

Other objects and advantages of the present invention will become apparent to those skilled in the art from a consideration of the following detailed description of one exemplary embodiment of the present invention, had in conjunction with the accompanying drawings, in which In accordance with the preslike numerals refer to 'like or wherein:

FIG. 1 is an exploded view of an embodiment of the invention, showing the commutator end of an armature .Of a dynamo-electric machine, the end frame of the machine, and means for mounting an abrading fabric on the end frame;

FIG. 2 is an elevation view of the end frame with the abrading fabric mounted thereon; and

FIG. 3 is a perspective view of the end. frame and abrading fabric mounted thereon, applied to the commutator of the dynamo-electric machine.

Referring to the drawings, to abrade the commutator of a dynamo-electric machine in accordance with the present invention, the end frame 13 of the housing of the machine, which is usually secured to the housing by corresponding parts, and

means of a pair of bolts in holes 15, 16,'is removed from the housing, whereupon the armature, represented by the numeral 10, is removed from the housing and mounted in any suitable holding device, such as a'conventional vise, not shown. The commutator of the armature is designated by the numeral 11, and the armature stub shaft adjacent the commutator is denoted by the numeral 12. When assembled within the dynamo-electric machine housing, the stub shaft 12 seats in bearing 14a located in the center of end frame 13, providing the axis upon which the armature rotates in the normal operation of the machine.

To equip the end frame 13 for abrading the commutator 11, slotted pins 17 and 23 are mounted on the end frame 13 through holes 15 and 16. Pin 17 has a threaded axial hole 19 in one end, and is affixed to the end frame by means of bolt 18 passing through hole 15 and threading into hole 19 of pin 17. Washers 20 and 21 may be used for spacers if necessary. Pin 17 is thus mounted on end frame 13, but is not tightened for reasons that will be apparent subsequently. Slotted pin 23 having an axial threaded hole 26, is similarly mounted on the end frame 13 by means of bolt 25 passing through hole 16, utilizing spacing washers 28 and 29 if necessary. Pin 23 is also not tightened in its mounting on frame 13.

Two strips of abrading fabric 31 and 32, such as emery cloth or sand paper, are arranged in face-to-face relation, with their abrading surfaces in contact, and one end of the double strip is inserted in slot 22 of pin 17, while the other end of the double strip is inserted in slot 27 of pin 23. The pins are then rotated until the abrading strips are Wrapped around their respective pins one or more turns, leaving enough slack in the strips, however, to permit their separation by an amount sufiicient to embrace the commutator 11. Bolt 18.is then tightened to fix pin 17 against rotation.

The assembly of end frame and abrading strips is then applied to the armature by locating the commutator 11 between the abrading surfaces of the two strips of abrading fabric and slipping the bearing 14a over the stub shaft 12. An axial spacer 30 may be employed in the bearing 14a if necessary to position the abrading strips in the desired axial position relative to the commutator. The pin 23 is then further rotatedruntil the desired tension is had on the strips to obtain an appropriate abrading pressure on the commutator, whereupon bolt 25 is tightened to clamp pin 23 against rotation.

Bolt 25 is provided with an axial extension 24 adapted to removably receive the handle 33 by means of axial bore 34 in the handle. Handle 33 is then used to rotate end frame 13 on shaft 12, causing the abrading strips 31 and 32 to rotate therewith and about the surface of the commutator 11, thereby applying a uniform abrading action over the entire surface of the commutator.

After the commutator 11 has received the desired amount of abrading, the end frame and abrading strip a) assembly are removed, and the spaces between the commutator segments are scraped clean, as may be effected by a serrated knife 35 which may be pivotally housed in a slot 36 in handle 33. Thereafter the commutator is cleaned of abrasive grit, as by an air blast, and the armature is returned to the dynamo-electric machine housing. The abrasive fabric strips 31 and 32, the pins and bolts 17, 18, 23, and 25, and the spacer 30 are all removed from the end frame, and it is returned'to the machine housing to reassemble the machine for use.

Accordingly it is seen that the present invention provides for the uniform abrading of a commutator, guided by the true center of the commutator as derived from the dynamo-electric machine itself, without recourse to expensive and complex mechanisms for truing and rotating the armature on its axial center. The present invention employs components of the machine itself to guide the abrading of the commutator accurately and uniformly over its circumference.

The foregoing specific example of the present invention is presented to enable a complete understanding of the invention, and it is understood that various modifications and variations will be apparent to those skilled in the art. For example: one strip of abrasive fabric may be used instead of; two; more than two strip holders could be employed to orient more than two strips of fabric circumambiently about the end frame; other types of fabric holders may be used; other means may be employed to removably clamp the fabric holders to the end frame; and other abrading means may be used, such as an abrasive block or a cutting or scraping type of abrader. Accordingly, those modifications and variations as are embraced by the spirit and scope of the appended claims are contemplated by the present invention, and are within the purview thereof.

What is claimed is:

1. In a dynamo-electric machine having a rotor, at commutator located at one end of said rotor, a housing for said machine including a separable end frame member adjacent said commutator, and support structure on said end frame member cooperating with support structure on said rotor forming a bearing for rotatively supporting said end of said rotor; the improvement consisting of a pair of slotted spaced holders removably mounted on said end frame member, a flexible abrasive web threaded in the slots of said spaced holders, said spaced holders being located on said end frame member to place said abrasive Web in pressure contact with the surface of said commutator when said support structures on said end frame member and on said rotor are placed in said bearing forming relationship, whereby the surface of said commutator is cleaned by said abrading means on relative rotation of said rotor and end frame member.

2. In a dynamo-electric machine as set forth in claim 1, a handle means removably mounted on said end frame for facilitating said relative rotation of rotor and end frame member.

3. In a dynamo-electric machine as set forth in claim 2, said end frame having holes through which it is securable to the remainder of said housing, and said holders being mounted on said end frame through said holes.

References Cited in the file of this patent UNITED STATES PATENTS 1,873,129 

1. IN A DYNAMO-ELECTRIC MACHINE HAVING A ROTOR, A COMMUTATOR LOCATED AT ONE END OF SAID ROTOR, A HOUSING FOR SAID MACHINE INCLUDING A SEPARABLE END FRAME MEMBER ADJACENT SAID COMMUTATOR, AND SUPPORT STRUCTURE ON SAID END FRAME MEMBER COOPERATING WITH SUPPORT STRUCTURE ON SAID ROTOR FORMING A BEARING FOR ROTATIVELY SUPPORTING SAID END OF SAID ROTOR; THE IMPROVEMENT CONSISTING OF A PAIR OF SLOTTED SPACED HOLDERS REMOVABLY MOUNTED ON SAID END FRAME MEMBER, A FLEXIBLE ABRASIVE WEB THREADED IN THE SLOTS OF SAID SPACED HOLDERS, SAID SPACED HOLDERS BEING LOCATED ON SAID END FRAME MEMBER TO PLACE SAID ABRASIVE WEB IN PRESSURE CONTACT WITH THE SURFACE OF SAID COMMUTATOR WHEN SAID SUPPORT STRUCTURES ON SAID END FRAME MEMBER AND ON SAID ROTOR ARE PLACED IN SAID BEARING FORMING RELATIONSHIP, WHEREBY THE SURFACE OF SAID COMMUTATOR IS CLEANED BY SAID ABRADING MEANS ON RELATIVE ROTATION OF SAID ROTOR AND END FRAME MEMBER. 